x/(3+x)=a

What about it ???

Making x the subject of the equation we get that 

\(x=a(3+x)\)

\(x=3a+ax\)

\(\frac{x}{x}=3a+\frac{ax}{x} \)

\(1=4a \)

\(\frac{1}{4}=a\)

Now we can solve for x

\(\frac{x}{3+x}=\frac{1}{4}\)

\(x=\frac{1}{4}(3+x)\)

\(x=\frac{3}{4}+\frac{x}{4}\)

\(4x=\frac{3}{4}+x\)

\(3x=\frac{3}{4}\)

\(x=\frac{1}{4}\)

Hi guest,

In your 3rd line you forgot to divide a by x

Plus what happens if x=0  you cannot divide by 0 ://

Very nice use of LaTex though :))

Oh i see thanks for pointing out my mistake!